This invention relates generally to extending life cycles of products, and more specifically to, methods and apparatus for removal of certain gases from enclosures.
At least one type of known ring laser gyroscope includes electrode seals having a thin layer of indium pressed between an electrode and a glass-ceramic block. Life testing of the gyroscopes has revealed that an effective life of the indium seals are shorter for samples tested in air, as opposed to samples tested in a dry nitrogen environment. In another test, the life of the indium seal was shorter for a sample tested in a higher humidity (water vapor) level, as compared to an indium seal sample located in a vacuum baked housing that was substantially sealed and having a dry nitrogen backfill.
It is believed that the shorter life of the indium seal is caused by corrosion of the seal originating at exposed outer diameters of the seal. The hypothesis has been supported by testing in an oxygen rich environment which shows that the corrosion moves radially inward from an outside diameter of the seal annulus. The corrosion can eventually breach the annular width of the seal and cause a leak between a low-pressure laser cavity, within the glass-ceramic block, and the ambient atmosphere. The leak eventually renders the gyroscope inoperative.
Current methods of reducing oxygen at the exposed outside diameter of an indium seal include vacuum baking a gyroscope housing to reduce humidity, backfilling the housing with dry nitrogen after the vacuum baking, and substantially sealing the housing. However, gases and humidity tend to penetrate the housing seals over the course of time, exposing the indium seals within the housing to air (oxygen) and humidity.